This is a large integrated version of mechanical principle and mechanical design, which is not as difficult as the separated version. For example. There are usually three methods for motion analysis of planar mechanisms, one is instantaneous center method, the other is graphical method, and the third is analytical method. The above three methods all mention the mechanical principle, and the basis of mechanical design is generally only the first one, the instantaneous center method. Graphical method needs the foundation of theoretical mechanics, and analytical method needs the foundation of complex variable function.